(2.08)

Now, we'll move on, to take a look inside the left ventricle. We'll remove this part of its wall. The mitral valve is here, the aortic valve is out of sight up here. This is the apex of the ventricle. This part of the ventricular wall forms the interventricular septum.

Here's the left ventricle in cross section. Here's the right ventricle. The interventricular septum is curved.

The left ventricle has a much thicker wall than the right, and it's circular in cross section, while the right ventricle is C-shaped. Here, we're looking backward into the mitral valve. To see it better, we'll return to the previous dissection, and go round to a view from behind. The mitral valve, also called the left atrio-ventricular valve, has two cusps. They're called the anterior cusp and the posterior cusp, though in reality they're more upper and lower.

Chordae tendineae from both cusps converge on two sets of papillary muscles: these on the poseterolateral wall of the ventricle, and these on the antero-medial wall. Here are the same papillary muscles, seen from the apex of the ventricle. Each group of papillary muscles sends chordae tendinae to each of the cusps of the mitral valve.

Here's the mitral valve in motion, seen from the apex of the left ventricle. Here are the papillary muscles, seen very close.

Above the mitral valve we're looking upward and backward along the outflow tract of the left ventricle towards the aortic valve.